Hmm, it’s been a while. 
I believe I placed them on a 50mm grid and I used 1/4-20 hardware. But I can double check when I get home. This is my build for your reference.
Hmm, it’s been a while. I believe I placed them on a 50mm grid and I used 1/4-20 hardware. But I can double check when I get home. This is my build for your reference.